The present invention relates to a thermal treatment catheter, and more particularly to a catheter having a thin outer wall and a defined fluid flow path within the outer wall to improve the effects of conductive cooling of the wall of the body conduit in which the catheter is inserted. The catheter of the present invention also incorporates a microwave energy-attenuating strip within the catheter which serves to attenuate microwave energy generated by the catheter in the direction of non-treatment tissues.
The prostate gland is a complex, chestnut-shaped organ which encircles the urethra immediately below the bladder. Nearly one third of the prostate tissue anterior to the urethra consists of fibromuscular tissue that is anatomically and functionally related to the urethra and the bladder. The remaining two thirds of the prostate is generally posterior to the urethra and is comprised of glandular tissue. The portion of the urethra extending through the prostate (i.e., the prostatic urethra) includes a proximal segment, which communicates with the bladder, and a distal segment, which extends at an angle relative to the proximal segment by the verumontanum.
Although a relatively small organ, the prostate is the most frequently diseased of all internal organs and is often the site of a common affliction among older men, benign prostatic hyperplasia (BPH), as well as a more serious affliction, cancer. BPH is a nonmalignant, bilateral expansion of prostate tissue occurring mainly in the transition zone of the prostate adjacent to the proximal segment of the prostatic urethra. As this tissue grows in volume, it encroaches on the urethra extending into the region of the bladder neck at the base of the bladder. Left untreated, BPH causes obstruction of the urethra which usually results in increased urinary frequency, urgency, incontinence, nocturia and slow or interrupted urinary stream. BPH may also result in more severe complications, such as urinary tract infection, acute urinary retention, hydronephrosis and uraemia.
Benign prostatic hyperplasia (BPH) may be treated using transurethral thermal therapy as described in further detail in U.S. Pat. No. 5,413,588 entitled DEVICE AND METHOD FOR ASYMMETRICAL THERMAL THERAPY WITH HELICAL DIPOLE MICROWAVE ANTENNA and in U.S. Pat. No. 5,575,811 entitled BENIGN PROSTATIC HYPERPLASIA TREATMENT CATHETER WITH URETHRAL COOLING, both of which are hereby incorporated by reference. During transurethral thermal therapy, the transition zone of the prostate is heated to necrose the tumorous tissue that encroaches on the urethra. Transurethral thermal therapy is administered by use of a microwave antenna-containing catheter which includes a multi-lumen shaft. The catheter is positioned in the urethra with the microwave antenna located adjacent to the hyperplastic prostatic tissue. Energization of the microwave antenna causes the antenna to emit electromagnetic energy which heats tissue within the prostate. A cooling fluid is circulated through the catheter to preserve tissue such as the urethral wall between the microwave antenna and the target tissue of the prostate.
The commercially available Targis(trademark) system from Urologix, Inc. of Minneapolis, MN employs a thermal therapy catheter that embodies the aforementioned U.S. Pat. No. 5,413,588, and is a product capable of performing thermal therapy of the prostate with microwave energy delivered from an applicator positioned in the urethra. The Targis(trademark) system has achieved substantial clinical and commercial success, indicating the efficacy of microwave thermal therapy for treating prostate disease. The success of the Targis(trademark) microwave thermal therapy system has led to continuing development efforts in the technology of thermal therapy catheters to further enhance the effects of microwave treatment of the prostate. One such development is disclosed in U.S. Pat. No. 6,161,049, entitled xe2x80x9cTHERMAL THERAPY CATHETERxe2x80x9d by E. Rudie, S. Stockmoe, A. Hjelle, B. Ebner and J. Crabb, which is hereby incorporated by reference. A further development is the subject of the present invention.
The present invention is a device and method for treating tissue adjacent to a body lumen such as a urethra. A catheter shaft having an outer surface is insertable into the body lumen, and the catheter shaft carries an energy-emitting element. The energy-emitting element is operable to radiate a generally symmetrical energy pattern. A plurality of cooling lumens in the catheter shaft around the energy-emitting element are configured for circulation of a fluid therethrough. An attenuating element is located in at least one of the plurality of cooling lumens. The attenuating element serves to attenuate energy in the direction of the non-treatment tissue, creating a radially asymmetrical thermal pattern in the tissue adjacent to the body lumen and thereby providing the capability to protect a designated region of healthy tissue from damaging amounts of thermal energy while permitting an increased depth of treatment of targeted tissues.